
public class OuShu {

	public static void main(String[] args) {
		long a=1;
		int sum=0;
while (a<=100) {
	if (a%2==0) {
		sum+=a;//sum=sum(0)+a;
		
	}
	a++;
	
}
	System.out.println(sum);	
		
		
		
	}

}
